Sharp Fickian Behavior of Electrogenerated Chemiluminescence Waves in Conjugated Polymer Films

One technique to study electrochemical oxidation phenomena in thin polymer films is the generation of electrogenerated chemiluminescence (ECL) waves. Such waves are sharp and easy to image, and recent experiments have shown both constant-speed and Fickian-style wave behavior. One way to model such waves mathematically is to track the concentration of the ion clusters in the polymer film. One such model has a standard Fickian form but with a highly nonlinear diffusion coefficient. This model is analyzed numerically, and the results are compared with previous asymptotic analysis. The results demonstrate that ECL waves corresponding to this model are indeed sharp and move in a Fickian way. Hence more complicated effects must be included in the model if constant-speed behavior is to be observed.